1. Field of the Invention
The present invention relates to an improvement in a color television camera usable both for bright scenery as well as dark scenery.
2. Prior Art
Sensitivity spectrums of color pickup devices such as pickup tubes generally have characteristic curves "a", "b", "c" or "d" as shown in FIG. 1, and some of them, especially of recent high sensitivity type, have considerable sensitivities in the infrared range as shown by the curves "b", "c" and "d" of FIG. 1. When such devices having considerable sensitivities are used in a color television camera, the infrared sensitivities are usually cut off by utilization of an infrared cut filter in order for faithful color reproduction. For such purpose, an infrared cut filter of transmission characteristic of curve "e" or "f" of FIG. 2 is generally used disposed in front of the image receiving face. Though such use of an infrared cut filter results in improvement of the color reproduced, when the scenery becomes dark, it will decrease pickup sensitivity of the image of the color television camera in comparison with the monochromatic television camera. In order to overcome such problem, a proposal has been made that a manually detachable infrared color filter is used in front of the color pickup device in order for performing an operation that the infrared filter is inserted when a color video signal is produced and the infrared filter is removed when a monochromatic video signal is produced, as disclosed in the Japanese unexamined patent publication Sho 52-129233 (129233/1977). However, such manually operated infrared filter is not practical for non-professional use, such as in visitor watching systems or in hobby video cameras wherein the operation should be as simple as possible in order to eliminate inadvertent maloperations leading to failures of image reproduction.